This invention relates to a copolymer emulsion, more particularly to an aqueous acrylic copolymer emulsion which can be cross-linked and cured by the oxygen in the air by adding a metal dryer thereto.
Recently, aqueous resins have been noticed from the viewpoint of causing no environmental pollution and saving resources. Particularly, aqueous emulsions are hopeful as coating resins, since they hardly use organic solvents, organic amines and the like. But almost aqueous emulsions contain thermoplastic resins, so that properties of coating film obtained therefrom are very inferior to those of coating film obtained from organic solvent-based resins, for example, in hardness, resistance to solvent, resistance to water, resistance to corrosion, and the like. Aqueous emulsions containing thermosetting resins have been developed but are not sufficient as general purpose coating resins, since in almost cases heating at a temperature of 130.degree. to 180.degree. C. or higher is necessary.
On the other hand, oxidation polymerization type alkyd emulsions are commercially available. But the alkyd emulsions are insufficient in drying at initial periods and further have problems in properties of coating film after cured, particularly in hardness and resistance to contamination.